refactor(theme): change default light theme to sepia

- Update default from paper-white to sepia for warmer reading
- Midnight remains default for dark mode
- Sepia provides warm, eye-friendly tones for light mode

src/components/Settings/ThemeSettings.tsx

@@ -11,7 +11,7 @@ interface ThemeSettingsProps {
 const ThemeSettings: React.FC<ThemeSettingsProps> = ({ settings, onUpdate }) => {
   const currentTheme = settings.theme ?? 'system'
   const currentDarkColor = settings.darkColorTheme ?? 'midnight'
-  const currentLightColor = settings.lightColorTheme ?? 'paper-white'
+  const currentLightColor = settings.lightColorTheme ?? 'sepia'
   
   // Determine which color picker to show based on current theme
   const showDarkColors = currentTheme === 'dark' || currentTheme === 'system'

src/hooks/useSettings.ts

@@ -54,7 +54,7 @@ export function useSettings({ relayPool, eventStore, pubkey, accountManager }: U
       applyTheme(
         settings.theme ?? 'system',
         settings.darkColorTheme ?? 'midnight',
-        settings.lightColorTheme ?? 'paper-white'
+        settings.lightColorTheme ?? 'sepia'
       )
       
       // Load font first and wait for it to be ready

src/services/settingsService.ts

@@ -50,7 +50,7 @@ export interface UserSettings {
   // Theme preference
   theme?: 'dark' | 'light' | 'system' // default: system
   darkColorTheme?: 'black' | 'midnight' | 'charcoal' // default: midnight
-  lightColorTheme?: 'paper-white' | 'sepia' | 'ivory' // default: paper-white
+  lightColorTheme?: 'paper-white' | 'sepia' | 'ivory' // default: sepia
 }
 
 export async function loadSettings(

src/utils/theme.ts

@@ -19,7 +19,7 @@ export function getSystemTheme(): 'dark' | 'light' {
 export function applyTheme(
   theme: Theme,
   darkColorTheme: DarkColorTheme = 'midnight',
-  lightColorTheme: LightColorTheme = 'paper-white'
+  lightColorTheme: LightColorTheme = 'sepia'
 ): void {
   const root = document.documentElement